Cards are a common organizing unit for modern user interfaces (UI). At their core, they’re just rectangular containers with borders and padding. However, when utilized properly to group related information, they help users better digest, engage, and navigate through content. This is why most successful dashboard/UI frameworks make cards a core feature of their component library. This article provides an overview of the API that bslib provides to create Bootstrap cards.
Setup code
To demonstrate that bslib cards work outside of Shiny (i.e., in R Markdown, static HTML, etc), we’ll make repeated use of statically rendered htmlwidgets like plotly and leaflet. Here’s some code to create those widgets:
library(bslib)
library(shiny)
library(htmltools)
library(plotly)
library(leaflet)
plotly_widget <- plot_ly(x = diamonds$cut) %>%
config(displayModeBar = FALSE) %>%
layout(margin = list(t = 0, b = 0, l = 0, r = 0))
leaflet_widget <- leafletOptions(attributionControl = FALSE) %>%
leaflet(options = .) %>%
addTiles()Shiny usage
Cards work equally well in Shiny. In the examples below, replace plotly_widget with plotlyOutput() and leaflet_widget with leafletOutput() to adapt them for Shiny server-rendered plots/maps.
Hello card()
A card() is designed to handle any number of “known” card items (e.g., card_header(), card_body(), etc) as unnamed arguments (i.e., children). As we’ll see shortly, card() also has some useful named arguments (e.g., full_screen, height, etc).
At their core, card() and card items are just an HTML div() with a special Bootstrap class, so you can use Bootstrap’s utility classes to customize things like colors, text, borders, etc.
card(
card_header(
class = "bg-dark",
"A header"
),
card_body(
markdown("Some text with a [link](https://github.com)")
)
)Some text with a link
Implicit card_body()
If you find yourself using card_body() without changing any of its defaults, consider dropping it altogether since any direct children of card() that aren’t “known” card() items, are wrapped together into an implicit card_body() call.1 For example, the code to the right generates HTML that is identical to the previous example:
card(
card_header(
class = "bg-dark",
"A header"
),
markdown("Some text with a [link](https://github.com).")
)Some text with a link.
Restricting growth
By default, a card()’s size grows to accommodate the size of it’s contents. Thus, if a card_body() contains a large amount of text, tables, etc., you may want to specify a height or max_height. That said, when laying out multiple cards, it’s likely best not to specify height on the card(), and instead, let the layout determine the height layout_column_wrap().
Although scrolling is convenient for reducing the amount of space required to park lots of content, it can also be a nuisance to the user. To help reduce the need for scrolling, consider pairing scrolling with full_screen = TRUE (which adds an icon to expand the card’s size to the browser window). Notice how, when the card is expanded to full-screen, max_height/height won’t effect the full-screen size of the card.
card(
max_height = 250,
full_screen = TRUE,
card_header(
"A long, scrolling, description"
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Amet felis fermentum viverra a pellentesque nulla potenti sociosqu nascetur sem. Placerat id curae vel diam; taciti ornare hac sapien fermentum lobortis. Elementum aenean eros dictumst ultricies pulvinar justo semper, ut magnis. Aliquam interdum cursus scelerisque blandit vulputate mattis odio, parturient nisl malesuada dignissim. Torquent iaculis aliquet curabitur litora dis vivamus quis!
Elit aliquam ac sed interdum in rutrum venenatis nisi rhoncus gravida – parturient eleifend nulla nullam. Tellus malesuada sed accumsan semper scelerisque. Ornare accumsan suspendisse posuere facilisi elementum cursus, blandit; taciti commodo facilisi lacinia? Fringilla id cursus ultricies conubia: rutrum torquent. Vehicula auctor himenaeos gravida aliquet vitae!
Sit magnis pulvinar, ante platea inceptos: ligula diam etiam. Penatibus nulla urna; fames mus, eleifend, dictumst, blandit egestas cursus. Sollicitudin tortor ligula sollicitudin vehicula quisque – est tortor libero elementum vehicula dapibus porta lectus. Congue ultricies donec vehicula est a est orci neque. Tempus dictum litora magna libero ligula primis tristique odio dapibus justo blandit at.
Filling outputs
A card()’s default behavior is optimized for facilitating filling layouts. More specifically, if a fill item (e.g., plotly_widget), appears as a direct child of a card_body(), it resizes to fit the card()s specified height. This means, by specifying height = 250 we’ve effectively shrunk the plot’s height from its default of 400 down to about 200 pixels. And, when expanded to full_screen, the plot grows to match the card()’s new size.
card(
height = 250,
full_screen = TRUE,
card_header("A filling plot"),
card_body(plotly_widget)
)Most htmlwidgets (e.g., plotly, leaflet, etc) and some other Shiny output bindings (e.g, plotOutput(), imageOutput(), etc) are fill items by default, so this behavior “just works” in those scenarios. And, in some of these situations, it’s helpful to remove card_body()’s padding, which can be done via spacing & alignment utility classes.
card(
height = 275,
full_screen = TRUE,
card_header("A filling map"),
card_body(
class = "p-0",
leaflet_widget
),
card_footer(
class = "fs-6",
"Copyright 2023 RStudio, PBC"
)
)Fill item(s) aren’t limited in how much they grow and shrink, which can be problematic when a card becomes very small. To work around this, consider adding a min_height on the card_body() container. For example, try using the handle on the lower-right portion of this card example to make the card taller/smaller.
This interactive example is a bit contrived in that we’re using CSS resize to demonstrate how to make plots that don’t shrink beyond a certain point, but this concept becomes quite useful when implementing page-level filling layouts (i.e., page_fillable()) with multiple cards.
card(
height = 300,
style = "resize:vertical;",
card_header("Plots that grow but don't shrink"),
card_body(
min_height = 250,
plotly_widget,
plotly_widget
)
)Troubleshooting fill
As you’ll learn more about in filling layouts, a fill item loses its ability to fill when wrapped in additional UI element that isn’t a fillable container. To fix the situation, use as_fill_carrier() to allow the additional element to carry the potential to fill from the card_body() down to the fill item.
Multiple card_body()
A card() can have multiple card_body()s, which is especially useful for:
- Combining both resizable and non-resizable contents (i.e., fill items and non-fill).
- Allowing each
card_body()to have their own styling (via inline styles and/or utility classes) and resizing limits (e.g.,min_height).
For example, when pairing filling output with scrolling content, you may want min_height on the filling output since the scrolling content will force it to shrink:
card(
height = 375,
full_screen = TRUE,
card_header(
"Filling plot, scrolling description"
),
card_body(
min_height = 200,
plotly_widget
),
card_body(
class = "lead container",
lorem::ipsum(paragraphs = 10, sentences = 5)
)
)Lorem euismod hendrerit sodales pharetra porta porttitor lobortis luctus primis feugiat! Ante dictumst eros, dis velit ullamcorper tristique odio quisque parturient, viverra congue scelerisque? Suspendisse semper sagittis integer imperdiet fames, quis parturient integer facilisis ornare! Ligula ante elementum leo turpis montes magna: risus dis euismod volutpat? Commodo ligula eu nec.
Amet bibendum, montes auctor arcu cursus in! Massa tellus, orci, lobortis litora molestie sem orci molestie fusce libero. Luctus suscipit imperdiet tincidunt augue – viverra velit potenti penatibus feugiat sociosqu quam. Maecenas orci urna accumsan sollicitudin morbi curae aliquet curabitur nisi. Fermentum lobortis inceptos rhoncus donec quisque, iaculis mollis non blandit lobortis fusce, sociis nunc suscipit, lectus consequat, dapibus accumsan id habitasse elementum!
Adipiscing risus luctus potenti, cras pellentesque mattis condimentum fringilla litora donec. Ultricies senectus sociosqu, rhoncus rhoncus tristique; potenti commodo tempor ultrices? Mollis erat maecenas tristique venenatis tempor aenean dui aliquam natoque. Aenean integer venenatis sem mus parturient: euismod torquent lacinia. Justo molestie velit eleifend inceptos, nullam orci penatibus!
Consectetur mauris erat est pulvinar dui penatibus hac risus interdum. Nostra tortor massa aenean metus pulvinar class velit. Per gravida turpis aliquet at. Leo cras molestie in himenaeos tellus vestibulum nibh quisque phasellus. Per vulputate odio cum cras placerat, feugiat sagittis placerat vestibulum lacus, vulputate gravida orci, in, hac cum mollis.
Adipiscing class sociis vitae fames, nibh nisl habitasse montes hendrerit ultricies? Interdum fringilla lobortis sodales himenaeos magna quam etiam nibh. Libero velit arcu vivamus montes nec duis tempor senectus. Porta porta augue lacinia potenti bibendum mollis eget. Vitae interdum praesent vivamus ullamcorper augue, tempus erat, per curabitur, rhoncus sociosqu felis!
Sit dictum fusce imperdiet porttitor elementum at vehicula semper vulputate suspendisse! Parturient iaculis nunc mattis ac a – interdum aptent enim tellus faucibus. Tortor tempor, semper, urna parturient eget aliquet curae. Dictumst magnis purus, nec mattis bibendum, vitae et. Vestibulum lacinia nibh cum elementum auctor, faucibus dui curabitur vel malesuada.
Adipiscing nulla eros – netus lobortis magnis, justo torquent penatibus sed. Nostra euismod vivamus sapien luctus scelerisque praesent penatibus mi himenaeos consequat! Accumsan gravida nostra erat faucibus litora metus faucibus sem! Convallis enim montes sed, dictum curae fusce? Mauris interdum fringilla semper velit nam euismod.
Lorem molestie eros gravida, odio id nam tortor cras. Tellus facilisis interdum sociis, parturient ante id? Rhoncus sociosqu fames lobortis ultrices interdum at mattis! Orci senectus eros consequat blandit. Scelerisque at dignissim tortor interdum non felis montes mollis nisl erat cursus eu natoque mattis justo, suscipit, etiam elementum odio.
Ipsum faucibus nisi, suscipit porta, vehicula mollis, malesuada fames cubilia ornare volutpat. Risus ultricies diam nisi bibendum ante morbi felis faucibus lectus eu. Urna netus dapibus cum conubia auctor inceptos nam venenatis? Dictum mollis risus sed, magnis purus, nibh massa eu conubia est. Congue himenaeos!
Lorem dictumst magna turpis massa sem pellentesque tristique bibendum. Fringilla tristique aptent curae et sagittis faucibus, potenti magna imperdiet turpis viverra. Neque massa sem cubilia nisi, sagittis integer nullam? Ultrices velit aenean rutrum purus aenean semper? Semper morbi ac faucibus scelerisque cras quisque potenti pellentesque ut sociis vel pretium semper tempus?
Also, when the content has a fixed size, and should not be allowed to scroll, set fill = FALSE:
card(
height = 350,
full_screen = TRUE,
card_header(
"Filling plot, short description"
),
plotly_widget,
card_body(
fill = FALSE,
card_title("A subtitle"),
p(class = "text-muted", "And a caption")
)
)A subtitle
And a caption
Multiple columns
As you’ll learn in column-based layouts, layout_column_wrap() is great for multi-column layouts that are responsive and accommodate for filling output. Here we have an equal-width 2-column layout using width = 1/2, but it’s also possible to have varying column widths.
card(
height = 350,
full_screen = TRUE,
card_header("A multi-column filling layout"),
card_body(
min_height = 200,
layout_column_wrap(
width = 1/2,
plotOutput("p1"),
plotOutput("p2")
)
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Lorem mi felis eros porttitor dui; sodales suscipit dui fringilla. Nam massa malesuada sed taciti ultricies urna ultricies iaculis. Libero cubilia cursus – consequat bibendum – blandit odio, odio netus etiam eros vehicula sociosqu laoreet. Velit viverra montes dui porttitor senectus nibh. Mi lobortis ligula commodo tristique dui, rhoncus euismod quam urna risus dictumst potenti orci erat.
Elit orci dapibus venenatis sociosqu magna; magna, duis potenti libero dictum ut torquent luctus natoque. Fames ornare, nulla blandit nascetur sociosqu sapien rutrum cras rhoncus facilisis mattis. Suscipit sociosqu facilisis montes ullamcorper commodo. Ornare inceptos imperdiet ante quam suspendisse, semper mi convallis dignissim tempor. Nam?
Lorem ligula platea class sodales duis placerat accumsan porttitor sociis faucibus quam. Curae vulputate mus semper eleifend porta leo facilisis. Sed felis sociis: ultricies auctor pulvinar maecenas ut sagittis nullam – nullam cubilia facilisis felis senectus! Mauris ullamcorper morbi potenti cum – cum, sem cras ante fringilla convallis? Cursus aliquet tortor cursus condimentum ante condimentum natoque, egestas, litora semper facilisi vulputate.
Multiple cards
layout_column_wrap() is especially nice for laying out multiple cards since each card in a particular row will have the same height (by default). Learn more in column-based layouts.
layout_column_wrap(
width = 1/2,
height = 300,
card(full_screen = TRUE, card_header("A filling plot"), plotly_widget),
card(full_screen = TRUE, card_header("A filling map"), card_body(class = "p-0", leaflet_widget))
)Multiple tabs
navset_card_tab() and navset_card_pill() make it possible to create cards with multiple tabs or pills. These functions have the same full_screen capabilities as normal card()s as well some other options like title (since there is no natural place for a card_header() to be used). Note that, each nav_panel() object is similar to a card(). That is, if the direct children aren’t already card items (e.g., card_title()), they get implicitly wrapped in a card_body().
library(leaflet)
navset_card_tab(
height = 450,
full_screen = TRUE,
title = "HTML Widgets",
nav_panel(
"Plotly",
card_title("A plotly plot"),
plotly_widget
),
nav_panel(
"Leaflet",
card_title("A leaflet plot"),
leaflet_widget
),
nav_panel(
shiny::icon("circle-info"),
markdown("Learn more about [htmlwidgets](http://www.htmlwidgets.org/)")
)
)Sidebars
As you’ll learn more about in sidebar layouts, layout_sidebar() just works when placed inside in a card(). In this case, if you want fill items (e.g., plotly_widget) to still fill the card like we’ve seen before, you’ll need to set fillable = TRUE in layout_sidebar().
card(
height = 300,
full_screen = TRUE,
card_header("A sidebar layout inside a card"),
layout_sidebar(
fillable = TRUE,
sidebar = sidebar(
actionButton("btn", "A button")
),
plotly_widget
)
)Static images
card_image() makes it easy to embed static (i.e., pre-generated) images into a card. Provide a URL to href to make it clickable. In the case of multiple card_image()s, consider laying them out in multiple cards with layout_column_wrap() to produce a grid of clickable thumbnails.
card(
height = 300,
full_screen = TRUE,
card_image(
file = "shiny-hex.svg",
href = "https://github.com/rstudio/shiny"
),
card_body(
fill = FALSE,
card_title("Shiny for R"),
p(
class = "fw-light text-muted",
"Brought to you by RStudio."
)
)
)Flexbox
Both card() and card_body() default to fillable = TRUE (that is, they are CSS flexbox containers), which works wonders for facilitating filling outputs, but it also leads to surprising behavior with inline tags (e.g., actionButton(), span(), strings, etc). Specifically, each inline tag is placed on a new line, but in a “normal” layout flow (fillable = FALSE), inline tags render inline.
card(
card_body(
fillable = TRUE,
"Here's some", tags$i("inline"), "text",
actionButton("btn1", "A button")
),
card_body(
fillable = FALSE,
"Here's some", tags$i("inline"), "text",
actionButton("btn2", "A button")
)
)That said, sometimes working in a flexbox layout is quite useful, even when working with inline tags. Here we leverage flexbox’s gap property to control the spacing between a plot, a (full-width) button, and paragraph. Note that, by using markdown() for the paragraph, it wraps the results in a <p> tag, which means the contents of the paragraph are not longer subject to flexbox layout. If we wanted, we could do something similar to render the actionButton() inline by wrapping it in a div().
card(
height = 325, full_screen = TRUE,
card_header("A plot with an action links"),
card_body(
class = "gap-2 container",
plotly_widget,
actionButton(
"go_btn", "Action button",
class = "btn-primary rounded-0"
),
markdown("Here's a _simple_ [hyperlink](https://www.google.com/).")
)
)Here's a simple hyperlink.
In addition to gap, flexbox has really nice ways of handling otherwise difficult spacing and alignment issues. And, thanks to Bootstrap’s flex utility classes, we can easily opt-in and customize defaults.
card(
height = 300, full_screen = TRUE,
card_header(
class = "d-flex justify-content-between",
"Centered plot",
checkboxInput("check", " Check me", TRUE)
),
card_body(
class = "align-items-center",
plotOutput("id", width = "75%")
)
)Shiny
Since this article is statically rendered, the examples here use statically rendered content/widgets, but the same card() functionality works for dynamically rendered content via Shiny (e.g., plotOutput(), plotlyOutput(), etc).
An additional benefit that comes with using shiny is the ability to use getCurrentOutputInfo() to render new/different content when the output container becomes large enough, which is particularly useful with card(full_screen = T, ...). For example, you may want additional captions/labels when a plot is large, additional controls on a table, etc (see the value boxes article for a clever use of this).
# UI logic
ui <- page_fluid(
card(
max_height = 200,
full_screen = TRUE,
card_header("A dynamically rendered plot"),
plotOutput("plot_id")
)
)
# Server logic
server <- function(input, output, session) {
output$plot_id <- renderPlot({
info <- getCurrentOutputInfo()
if (info$height() > 600) {
# code for "large" plot
} else {
# code for "small" plot
}
})
}
shinyApp(ui, server)Appendix
The following CSS is used to give plotOutput() a background color; it’s necessary here because this documentation page is not actually hooked up to a Shiny app, so we can’t show a real plot.